1. Field of the Invention
This invention relates to an opening-closing mechanism by which an automatic original feeding apparatus for a copier or the like for automatically placing or discharging an original onto or from a platen is opened and closed relative to the platen.
This invention also relates to an opening-closing mechanism for an original pressing plate for pressing an original placed on the original supporting table of an original reading apparatus.
2. Related Background Art
When an original is to be copied in a copying apparatus having an automatic original feeding apparatus mounted thereon, the original can be automatically copied by using the automatic original feeding apparatus or the original can be manually placed at a predetermined position and copied without using the automatic original feeding apparatus.
That is, when an automatic original feeding apparatus is used, a desired original is placed on the original tray 22 of an automatic original feeding apparatus 21 as shown, for example, in FIG. 10 of of the accompanying drawings, and when the start key 30 of a copying apparatus 20 is depressed, the original is automatically conveyed to and placed on the platen glass 23 of the copying apparatus which is a portion for reading an image, by a white belt 25 or the like, and when the original is stopped at a predetermined position, the optical system (not shown) of the copying apparatus 20 scans the original, whereby image formation is effected. When the reading of the image of the original is terminated, the original is discharged from the platen glass by the white belt 25 and is again placed on the original tray 22. A series of these operations will be automatically performed if the automatic original feeding apparatus is used.
On the other hand, when the automatic original feeding apparatus is not used and an original is to be manually placed on the platen glass 23, the automatic original feeding apparatus is opened in such a manner as to be raised in a direction away from the platen glass 23 as shown in FIG. 11 of the accompanying drawings, and the original is placed at a predetermined position on the platen glass, and then the automatic original feeding apparatus 21 is closed from above so that the surface of the original may be brought as close as possible to the platen glass 23, whereafter the start key 30 of the copying apparatus 20 is depressed to thereby effect image formation.
As shown, an opening-closing device (hinge) 24 for enabling the automatic original feeding apparatus 21 to be opened and closed is mounted on the automatic original feeding apparatus 21, and a spring for biasing the automatic original feeding apparatus in an opening direction is disposed in the hinge so that the automatic original feeding apparatus 21 can be easily opened particularly when it is to be opened in a raising direction, and thus the weighty automatic original feeding apparatus 21 can be raised smoothly. Also when the automatic original feeding apparatus is to be closed, the dropping speed of the automatic original feeding apparatus by its gravity may be suppressed to some extent by the action of the above-described spring so that the automatic original feeding apparatus may quietly land on the platen glass 23.
In the above-described example of the prior art, however, the automatic original feeding apparatus, as is well known, has disposed therein a conveying roller, a discharge roller, a paper guide, a driving motor, etc., all not shown, for automatically feeding and placing the original on the original tray onto a predetermined position on the platen, and discharging the original from the platen and again placing the original onto the original tray upon completion of the copying operation of the copying apparatus and therefore, it is considerably weighty and thus, much load is applied to the spring for biasing the automatic original feeding apparatus in the raising direction. Particularly, when the automatic original feeding apparatus is used for a long time, the ability of the spring is reduced and the spring becomes unable to provide its original spring force, and this has led to the disadvantage that when the automatic original feeding apparatus is closed, the dropping speed thereof increases and the apparatus is damaged or the platen glass is damaged by the shock when the apparatus lands on the platen glass.
Also, there has been the disadvantage that even though the ability of the spring of the hinge is not reduced, when a user forcibly closes the automatic original feeding apparatus, the apparatus is damaged by the shock when it lands on the platen glass.
Also, depending on an image forming apparatus, use is made of an image forming apparatus provided in advance with only an automatic original feeding apparatus for automatically feeding an original to the original supporting table of the image forming apparatus in order to enhance the efficiency of the copying work when a plurality of original sheets are to be copied. Also, there are known an image forming apparatus and an automatic original feeding apparatus for constructing the automatic original feeding apparatus mountably on the image forming apparatus later in order to achieve the high efficiency of the copying work for a user who has bought only the image forming apparatus.
However, with an apparatus of a construction in which a user having an image forming apparatus in advance mounts an automatic original feeding apparatus later on the image forming apparatus or a serviceman assembles an automatic original feeding apparatus to the image forming apparatus at the user's, it is difficult to align the original supporting table of the image forming apparatus and the automatic original feeding apparatus with each other in order to ensure the stable conveyance of originals, and this has led to the disadvantage that the serviceman requires much time and labor to mount the automatic original feeding apparatus on the image forming apparatus.